The evolved UMTS Terrestrial Radio Access Network (UTRAN) which provides the radio interface in the third generation Partnership Program (3GPP) Long Term Evolution (LTE) architecture consists of radio base stations eNB, providing the evolved UTRAN User Plane (U-plane) and Control Plane (C-plane) protocol terminations towards a User Equipment (UE). The eNBs are interconnected with each other by means of the X2 interfaces. It is assumed that there always exist an X2 interface between the eNBs that need to communicate with each other, e.g., for support of handover of UEs in LTE_ACTIVE mode. This is further defined in 3GPP release 12.
FIG. 1 generally depicts a configuration in an LTE network architecture. FIG. 1 shows the X2 interfaces 16 between the eNBs and also the S1 interfaces 17 between the eNBs and the Mobility Management Entity (MME) and Serving Gateway, (S-GW).
The X2 interface is used for control plane traffic and optional forwarding of user plane traffic during handover. There is also provision for an S1-based handover but is typically only employed as a fallback option when the X2 interface is not available. Current estimates indicate that the combined X2-c and X2-u traffic could be between 4 and 10 percent of the core-facing bandwidth over the S1-u interface and the delay should be less then 30 ms. This traffic is typically important and from future releases in LTE Advanced, it is envisaged that more user plane traffic will traverse the S1-u interface. Also in Release 11 there will be stringent latency requirements necessary to implement features such as collaborative Multiple Input Multiple Output (MIMO) and Coordinated Multi Point (CoMP).
The connectivity between eNBs can be provided by the means of Layer 3 (L3) connectivity services. For this purpose, the deployment of Internet Protocol/MultiProtocol Label Switching (IP/MPLS) network elements connecting eNBs is required. In the alternative, the L3 connectivity end point can be implemented at or close to the S-GW site, but this can be associated with some drawbacks: First it may introduce too high communication latency and loading the typically bandwidth-limited backhaul link with inter-eNB traffic. Second implementing L3 end points directly on the backhaul network connecting eNBs, may introduce a too high configuration/provisioning complexity as the operator will have a much higher number of configuration points compared to the centralized solution.
In both cases a rather static configuration of the L3 end points will typically be the most viable option in order to avoid an even higher configuration complexity, which in turn can cause sub-optimal resource utilization and some pairs of eNBs not directly connected.
Hence, there is a need for a method and an apparatus that provide an improved utilization of resources in a cellular radio network, in particular an LTE radio network.